write new pallet that supports multiple currencies

[brenzi]

pallet-balances only supports a single currency. We'll need to map CurrencyIdentifier to different balances
This pallet shall later support demurrage

The node would still have a standard balances module for xt fees (the NCTR token in Cantillon testnet)

one option is to use generic-asset and write a wrapper for demurrage.

Do not integrate this in encointer-currencies, because that will live transparently on-chain

Check this out too: https://github.com/laminar-protocol/open-runtime-module-library/tree/master/currencies

• Implement MultiCurrency
• like Token

[brenzi]

done: https://github.com/encointer/pallet-encointer-balances